Research On Sharing Techniques Of USB Devices In Network Environments

USB (Universal Serial Bus) is an emerging peripheral bus standards, with advantages of plug-and-play, rapid and reliable data transmission, facilitate expansion, low cost, low power consumption, has now become an essential computer interface, and it also has been widely used in embedded systems.Along with the gradual expansion of USB applications, in order to share the USB devices in IP network for improving the efficiency and availability, it is hoped the combining of the two technologies: USB and the IP network. However, the existing USB protocols and drivers can't meet the demand. To solve the above problem, on the foundition of further studing the existing USB device sharing technologies, this paper proposed a new USB device sharing technology based on C/S Structure, namely USBoIP(USB over IP).The research topic not only has the theoretical value, i.e. first, extending the USB to IP network, which makes up for the inadequacy of the existing USB drivers; Second, improving the existing network protocol algorithms in order to ensure the quality of services of the USB packet transmission in IP Network. Meanwhile, it also has wide applications, including domains of the enterprise office, the household control and the industrial control. Moreover, accessing the USB device through IP network is in keeping with the trend of 'Network Everywhere'.In reference to the existing bus sharing technologies, we designed a feasible USB device sharing software structure that had the advantages of extensibility and network transparency, and implemented it on Linux.In addition, as good transmission qualities will materaliaze the virtues of rapidness and reliability of USB, we also studied the issues on the quality of service about USB packet transmission in IP network. Through the research on the TCP/IP protocol, we found that congestion control algorithm played an important role in the performance of data transmission in Network. Then, we went deep into the studies of congestion control algorithms in the IP network. And according to the characteristics of data transmission in USB and taking into account the facters of reliability, real-time, packet size, priority etc of USB, we designed different congestion control algorithms for different types of USB transmission with the idea of Differentiated Service.1. Control and Interrupt TransmissionThat had the characteristics of reliability and small amount of data. We improved the start algorithm of TCP and proposed the 'Adaptive-Start' algorithm, which was suitable for small data packet transmission.2. Isochronous TransmissionThat had the characteristics of high-priority, real-time, unreliable. First, throuth the study of the process of TCP Congestion Controls, we deduced the 'TCP Throughput Model' which was considering of the slow-start phase; Then, based upon the TCP Throughput model, we designed a simple rate-based TCP friendly congestion control algorithm (SimTFCC), which was used to transmit real-time USB packets.Finally, the NS simulation proved that the above algorithms had a good performance of USB data packets transmission in the network.